The present invention relates to tobacco processing machines in general, and more particularly to improvements in apparatus which can be used in such machines to make rod-like tobacco fillers.
Cigarette making machines are equipped with means for forming a continuous stream of tobacco particles and with means, known as a trimming or equalizing device, for removing the surplus or excess from the stream so that the remainder of the stream forms a rod-like filler which is ready to be compacted and wrapped into a web of cigarette paper or the like. The resulting cigarette rod is thereupon severed at regular intervals to yield a file of plain cigarettes of unit length or multiple unit length. The thus obtained cigarettes are transported into storage, to a filter tipping machine or directly to a packing machine.
Many presently known cigarette rod making machines employ a tobacco stream forming unit wherein particles of tobacco are showered into elongated tobacco channel having an elongated bottom wall constituting one reach of an endless flexible air-permeable conveyor which gathers the particles into a continuous stream and transports the resulting stream lengthwise between two stationary sidewalls of the channel. That side of the bottom wall which faces away from the sidewalls is adjacent to a suction chamber serving to attract the stream to the bottom wall and to ensure that the particles of the stream advance with the bottom wall in a direction toward the wrapping station. The excess is removed by a trimming device which is normally mounted for movement toward and away from the bottom wall so as to remove from the stream a variable amount of tobacco with the result that the remainder of the stream forms a continuous rod-like filler containing a desired quantity of tobacco per unit length. The just described apparatus can be used for the making of fillers from natural or reconstituted tobacco as well as from substitute materials in admixture to or without natural tobacco. The articles which are produced can constitute plain cigarettes, cigars or cigarillos.
As a rule, the position of the trimming device with reference to the bottom wall of the tobacco channel is varied in dependency on one or more variable parameters, such as the density of the filler. Reference may be had, for example, to commonly owned U.S. Pat. No. 4,280,516 granted July 28, 1981 to Joachim Reuland. Such mode of regulating the quantity of tobacco in the filler is quite acceptable because the density of the filler can be changed with a minimum of delay. However, it has been found that the weight of finished products (such as plain cigarettes of unit length) fluctuates considerably as a result of changes in the position of the trimming device in response to signals from a density monitoring device. The fluctuations are especially pronounced when the trimming device is moved to a position at a substantial distance from the bottom wall of the tobacco channel, i.e., to a position in which the rate of removal of the excess from the continuous tobacco stream is minimal. In other words, the unpredictability of characteristics of the ultimate product is more pronounced when the trimming device is moved to a position in which it removes a relatively small quantity of tobacco particles. Moreover, the fluctuations are more pronounced when the extent of adjustment of the trimming device is substantial, e.g., when the tobacco engaging and removing components of the trimming device are moved from positions very close or rather close to the bottom wall to positions at a much greater distance from such bottom wall.